In an Oct. 16 letter, four Cornelius officers alleged "ongoing corruption" in the police department and claimed that Rubenstein along with Assistant Chief Joe Noffsinger have covered up officer misconduct and created a "hostile and adversarial work environment." Sgt. Shawn Watts and officers Doug Schuetz, Mark Jansen and Miguel Monico signed the letter.

Rubenstein declined to comment on the letter.

City Manager Rob Drake on Tuesday will announce an interim chief. Until then, Noffsinger will lead the department, according to the city.

The city says it anticipates the internal investigation to last for several weeks.

Following The Oregonian's request for the letter Friday, the city issued a press release Tuesday stating that the Local Government Personnel Institute is helping with the city's investigation. Drake said prior to the request that the city had not planned to release the letter because officials cannot talk about the ongoing investigation.